The present invention relates to a device and a method for sound wave communication, which transmit and receive sound waves to exchange data.
To activate games and chatting using near field communication such as Wi-Fi, Bluetooth or the like, a near field communication method that can be used only through software download without adding a separate device is needed in almost all mobile communication terminals currently used in public. From a viewpoint that a mobile communication terminal is basically provided with a voice communication function, communication using sound waves may be an effective alternative.
Further, in many cases, sound wave communication may implement low power communication in comparison with RF communications such as Bluetooth and the like. A sound wave communication is disclosed in U.S. Pat. No. 5,848,027 filed by Biometrics, Inc. The patent discloses a method and a system for transmitting digital data to a personal computer (PC) using beep sounds of a portable terminal such as a digital display wrist watch or the like.
This system uses Continuous Waveform (CW) modulation such as Binary Frequency Shift Keying (BFSK) modulation, Amplitude Shift Keying (ASK) modulation or the like.
The BFSK modulation is a method of allocating ‘0’ and ‘1’ to sound waves of two specific frequencies respectively, and the CW modulation is a method of allocating ‘1’ if a sound of a specific intensity or higher is continued for a specific time period and allocating ‘0’ if a state without a sound is continued for a specific time period regardless of frequency. A communication performed in such modulation methods may transmit only data of 1 bit on two types of sound waves during a specific unit time.
Since sound waves used in a general mobile communication terminal has a considerably low frequency compared with radio waves, a unit time, which is a time for distinguishing data arrays to be transmitted, is quite long compared with the radio waves. Accordingly, if only 1 bit is transmitted during a unit time using only two types of sound waves as shown in U.S. Pat. No. 5,848,027, the transmission speed will be apparently low.
To solve such a problem, a communication method using sound waves having a variety of frequency sounds, rather than using only the two types of sound waves, has been proposed. That is, the communication is accomplished by determining a sound pitch frequency used for music as a frequency sound used for the communication, matching a data digital value to each sound pitch frequency, and transmitting and decoding various frequency sounds. In this manner, a plurality of bits is transmitted per unit time.
However, in performing the sound wave communication using binary bits or bits exceeding the binary bits as described above, there is a disadvantage in that hardware characteristics are not considered. That is, there may be a problem in that when a sound wave is transmitted through a speaker, the sound wave may be transmitted on another frequency having a slight error, not a reference frequency originally set according to the hardware characteristic of the speaker, and since a microphone receiving the sound wave demodulates the original reference frequency, a correct data may not be received.
Further, an existing sound wave communication has a problem in that since there is no reference for separating data when signals different from each other are generated in the same region due to the characteristic of the sound wave, a data cannot be received when a plurality of sound waves are duplicated.